274 Researches on some important Points 



tibles, quantities of heat very different from what would be pro- 

 duced by a weight of gaseous oxygen equal to that which they 

 contain. This fact, which ought to have excited doubts respect- 

 ing the first explanation, only restricted its generality : it was 

 then supposed that the oxygen, in certain combinations, was ca- 

 pable of retaining a dose of caloric almost as great as that which 

 it contains in the elastic state. Later observed facts could not be 

 explained according to the theory^ without admitting that oxy- 

 gen in certain combinations retained a quantity of heat even su- 

 perior to what it contains when in the elastic state: such are the 

 detonations produced by mixtures of chlorate of potash with 

 certain combustibles, or the spontaneous explosions of Davy's 

 euchlorine, and of the chloroide and iodide of azote. 



This mode of explanation was afterwards extended to all com- 

 binations. It was considered as a principle sufficiently established, 

 that a body, in combining vvith a certain number of others, might 

 abandon a greater or less portion of its heat, according as, in 

 each case, the different degrees of affinity of the elements in con- 

 tact occasioned the molecules to approach more or less nearly to 

 each other. It is the degree of this approach, essentially vari- 

 able, that has been designated by the word condevsation, so fre- 

 quently employed by chemists. This is the theory adopted al- 

 most generally in France. Several foreign chemists have pointed 

 out its inaccuracy, and modified it in several points, but without 

 producing any conclusive proof, either against the opinion which 

 they combat, or in support of that which they would substitute. 



It thus appears that the different explanations relative to the 

 development of heat, in chemical combinations, are reducible to 

 simple assertions derived from the first hypothesis of Lavoisier: 

 and it is wonderful that, since this doctrine was first proposed, it 

 has not been more closely examined ; and that, even from the re- 

 sults already known, all the arguments which they are capable of 

 furnishing against it have not been drawn from them. The re- 

 lations which we have pointed out between the specific heats of 

 simple bodies and those of their compounds, preclude, we think, 

 the possibility of supposing that the heat developed by chemical 

 actions owes its origin merely to the heat produced by changes 

 of state, or to tiiat supposed to be combined with the material 

 molecules. We have even a better reason for rejecting this purely 

 gratuitous hypothesis, as we can explain the phaenomenon in a 

 manner more satisfactory. In fact, Davy has long ago shown that 

 when the two poles of a Voltaic pile are united by means of pieces 

 of charcoal placed in a gas incapable of supporting combustion, 

 the charcoal may be kept in a state of strong ignition as long as 

 the pile remains in activity, and without the charcoal undergoing 

 any chemical change. On the other hand, we are warranted to 



conclude. 



